New evidence from the Centers for Disease Control and Prevention this morning points to the ongoing and significant drop in the U.S. teen birth rate over the past 2o-plus years. The birth rate for teenagers ages 15-19 was 26.6 births per 1,000 in 2013, down 57 percent from the rate of 61.8 births per 1,000 in 1991, according to the CDC's National Center for Health Statistics.

The CDC attributes the 20-year decline to decreased sexual activity among teens, as well as more frequent use of contraception. As you would imagine, this historic decline in the teen birth rate has looked differently across states, races and age. The CDC report highlights some important ways in how this decline hasn't played out quite evenly.

The age difference

The birth rates for the 10-14, 15-17 and 18-19 age brackets were all at record lows in 2013. The decline has been much greater though, for girls 15-17. The 12.3 birth per 1,000 rate for teens 15-17 fell 68 percent since 1991, compared to 50 percent for teens 18-19, whose rate is 47.3 births per 1,000. More recently, the decline in birth rates since 2007 has also been greater for the 15-17 group (43 percent compared to 34 percent).

(National Center for Health Statistics)

Which groups have seen the biggest declines?

The teen birth rate has declined across all racial groups since 1991, but the steepest declines have been recorded among Asian-Pacific Islanders (64 percent) and non-Hispanic blacks (63 percent). API teens currently have the lowest birth rate overall (9.7 per 1,000), while Hispanic teens have the highest rate among the racial groups (46.3 percent). Still, the rate for Hispanic teens has fallen the fastest since 2007 (39 percent), and the CDC notes that the birth rates across most racial and Hispanic ethnicity groups is narrowing, as the following chart shows:

(National Center for Health Statistics)

Uneven declines across the states

States have taken different approaches to reducing teen births, with differing results. Every state has seen a decline since 1991, but rates continue to be lowest in the Northeastern states and higher in the South. New England states all had teen birth rates under 20 per 1,000, with New Hampshire's the lowest at 13.8. Eight states had rates above 40 per 1,000, with New Mexico recording the highest at 47.5. The District of Columbia joined four states in seeing declines of more than 60 percent since 1991.

The United States could do better

The good news for America is somewhat tempered by the fact that our teen birth rate still ranks among some of the highest for developed countries. While countries like Denmark, Switzerland and Japan recorded teen birth rates under 5 per 1,000, the United States finds itself among seven of 31 countries highlighted by the CDC with rates exceeding 20 births per 1,000 teens.

What the U.S. progress means

Though the United States lags behind other countries, the CDC says the progress made since 1991 has amounted to 4 million fewer teen births. Citing research from the National Campaign to Prevent Teen and Unplanned Pregnancy, the CDC says this also saved taxpayers an estimated $12 billion alone in 2010 from costs associated with government-funded health care, child welfare and higher incarceration rates for the children of teen moms. And having fewer babies born to teen mothers, the CDC points out, is good for other reasons. Teen motherhood comes with a higher health risk for the baby, educational limits for the mother and limited resources, since about 90 percent of teen births are to unmarried mothers. And babies born to teen mothers are more likely to eventually become teen mothers themselves.

Correction: An earlier version of this story said teenage mothers had higher incarceration rates. It's actually the children of teenage mothers with higher incarceration rates.

Jason Millman covers all things health policy, with a focus on Obamacare implementation. He previously covered health policy for Politico.

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